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10/01/2021 Ephemeris – Learn about exoplanets and have a star party tonight (virtually)

October 1, 2021 Comments off

This is Bob Moler with Ephemeris for Friday, October 1st. Today the Sun will be up for 11 hours and 41 minutes, setting at 7:22, and it will rise tomorrow at 7:42. The Moon, 3 days past last quarter, will rise at 2:49 tomorrow morning.

The Grand Traverse Astronomical Society hold a virtual meeting and program at 8 pm tonight via Zoom. For the program, yours truly will present Finding Exoplanets. Exoplanets are planets found orbiting other stars or rogue planets floating in interstellar space alone. We’ve actually only seen a handful of exoplanets, so most are detected by their effects on their host star. A virtual star party will start around 9 pm, hosted by Dr. Jerry Dobek, astronomy professor at Northwestern Michigan College, but only if it’s clear in Traverse City. It will feature Jupiter and Saturn, wonders of the northern part of the summer Milky Way. Instructions to join the meeting and a link can be found on the society’s website, http://www.gtastro.org.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4 hours). They may be different for your location.

Addendum

Finding Exoplanets title slide

Finding Exoplanets title slide.

07/23/2021 – Ephemeris – The first exoplanet* found

July 23, 2021 Comments off

This is Bob Moler with Ephemeris for Friday, July 23rd. Today the Sun will be up for 14 hours and 58 minutes, setting at 9:18, and it will rise tomorrow at 6:20. The Moon, at full today, will rise at 9:35 this evening.

In 1995 the first planet was found that orbits another star. It was 51 Pegasi b. That’s the star labeled number 51 in the constellation Pegasus, the flying horse. It was found because it tugged on its star as it orbited it. The planet was detected by the Doppler method, the same method that the police can tell if you’re speeding. A planet doesn’t orbit the center of the star, but the center of their combined mass. It turned out That 51 Pegasi b is a very large planet, half the mass of Jupiter, orbiting its star every 4 ½ days. Its discovery threw everything we thought we knew about planetary system evolution into a cocked hat. Planets just don’t stay nicely in their orbits like we thought. They move in and out! As this planet moved in toward its star, it would have ejected any of the inner planets out of the system.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

* A planet was found several years before, orbiting a pulsar, which is a neutron star. Apparently, planets orbiting dead stars don’t count.

Addendum

Pegasi 51b artist's visualization

An artist’s depiction of what exoplanet Pegasus 51b and its star might look like. Credit: ESO (European Southern Observatory) / M. Kornmesser.

11/25/2019 – Ephemeris – Fomalhaut has a visible exoplanet

November 25, 2019 Comments off

Ephemeris for Monday, November 25th. Today the Sun will be up for 9 hours and 14 minutes, setting at 5:06, and it will rise tomorrow at 7:53. The Moon, 1 day before new, will rise at 7:41 tomorrow morning.

The lonely bright star low in the south at 8 p.m. these evenings is Fomalhaut the harbinger of autumn in my book, and about to leave as winter approaches. Fomalhaut means fishes mouth and is located at the head of Piscis Austrinus, a very dim constellation. Fomalhaut is a young white star only about 400 million years old with a disk of dust surrounding it. Near an outer dust ring, 15 years ago the Hubble Space Telescope discovered a spot. Four years later astronomers discovered that the spot moved along the dust lane and announced the first direct discovery of an exoplanet. In 2010 and 2012 the planet now dubbed Fomalhaut b or Dagon was observed again and it really does orbit Fomalhaut in a very eccentric orbit.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Fomalhaut in the south at 8 p.m. on November 15, 2012. Created using Stellarium.

Fomalhaut in the south at 8 p.m. in November. Created using Stellarium.

Fomalhaut b

The track of observations of Fomalhaut b or Dagon in 2004, 2006, 2010 and 2012. Credit: NASA and ESA – http://www.nasa.gov/images/content/717874main_p1301aw-orig_full.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=23735991

11/20/2018 – Ephemeris – Barnard’s Star has a planet

November 20, 2018 Comments off

Ephemeris for Tuesday, November 20th. The Sun will rise at 7:46. It’ll be up for 9 hours and 23 minutes, setting at 5:10. The Moon, 3 days before full, will set at 5:37 tomorrow morning.

One of the most fascinating stars in the sky is Barnard’s Runaway Star. That’s how I first knew it. It’s now simply Barnard’s Star. It has the largest motion of any star across the sky (proper motion) of 10.3 arcseconds per year. That’s about the current width of Mars right now in telescopes. The Sun and Moon are about eighteen hundred arcseconds in diameter. It was announced last week, that a planet has been discovered orbiting that star. The planet designated with a lower case b orbits the red dwarf star at a distance comparable to Mercury in our solar system with a period of 233 days. It is three and a quarter times the Earth’s mass. It was found because it changes the velocity of the stars’ approach by the human walking speed in those 233 days.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Barnard Star's proper motion
Barnard Star’s proper motion from 1985 to 2005. Credit Steve Quirk.

I recall back in the 1960’s astronomer Peter van de Kamp announced the discovery of a planet around Barnard’s Star.  His technique was to spot little wiggles in the star’s path through the sky.  Current methods to detect wiggles of the star use the Doppler method  detecting the tiny change in the star’s radial velocity towards or away from us.  Barnard’s Star b does not fit what van de Camp thought he detected.

The star gets its name from Edward Emerson Barnard ( 1857-1923) who discovered the star’s rapid proper motion. 

On a local note Barnard’s great photographic work A Photographic Atlas of Selected Regions of the Milky Way was republished by my friend Gerold O. Dobek, Professor of Astronomy, Northwestern Michigan College and Director of its Joseph H. Rogers Observatory. 

11/27/2017 – Ephemeris – Ross 128b the second closest known exoplanet

November 27, 2017 1 comment

Ephemeris for Monday, November 27th. The Sun will rise at 7:54. It’ll be up for 9 hours and 10 minutes, setting at 5:05. The Moon, 1 day past first quarter, will set at 1:37 tomorrow morning.

The second closest exoplanet to the solar system has been discovered. That was earlier this year around a star named Ross 128. It’s name is Ross 128 small letter b. The star Ross 128 is a nearby red dwarf star, whose distance is a shade under 11 light years away, The star is thought to be twice the age of the Sun, We’d be in big trouble if the Sun were that old, but Ross 128 is just getting started. The exoplanet is about 35% more massive than the Earth. It’s distance from the star averages 4.6 million miles and its year is a bit under 10 Earth days. At that rate I’d be over 28 hundred years old. Astronomers don’t know the size or the density of the planet since it doesn’t pass in front of its star. These measurements will have to wait on larger telescopes.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Ross 128

The star Ross 128. It’s actually much fainter than is suggested here in the diagram from Sky and Telescope magazine’s website.. Mars’ position is for November 2017.

11/24/2017 – Ephemeris – Fomalhaut, the loneliest star, has a little buddy

November 24, 2017 1 comment

Ephemeris for Friday, November 24th. The Sun will rise at 7:51. It’ll be up for 9 hours and 15 minutes, setting at 5:07. The Moon, 2 days before first quarter, will set at 10:30 this evening.

The lonely bright star low in the south at 8 p.m. these evenings is Fomalhaut the harbinger of autumn in my book, and about to leave as winter approaches.  Fomalhaut means fishes mouth and is located at the head of Piscis Austrinus, a very dim constellation.  Fomalhaut is a young white star only about 400 million years old with a disk of dust surrounding it.  Near an outer dust ring, 15 years ago the Hubble Space Telescope discovered a spot.  Four years later astronomers discovered that the spot moved along the dust lane and announced the first direct discovery of an exoplanet.  In 2010 and 2012 the planet now dubbed Fomalhaut b or Dagon was observed again and it really does orbit Fomalhaut in a very eccentric orbit.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Fomalhaut in the south at 8 p.m. on November 15, 2012. Created using Stellarium.

Fomalhaut in the south at 8 p.m. on November evenings. Created using Stellarium.

Fomalhaut b

Fomalhaut b and it’s path around its star. Credit: NASA, ESA, and P. Kalas (University of California, Berkeley and SETI Institute)

03/06/2017 – Ephemeris – TRAPPIST-1 The star with seven earth-sized planets

March 6, 2017 Comments off

Ephemeris for Monday, March 6th.  The Sun will rise at 7:10.  It’ll be up for 11 hours and 26 minutes, setting at 6:37.  The Moon, 1 day past first quarter, will set at 3:47 tomorrow morning.

The big astronomical news of two weeks ago was the announcement of a star system that had at least 7 earth-sized planets.  And that three of them were in the habitable zone of their dim red dwarf star.  The designation of the star is TRAPPIST-1, a Belgian telescope in South America that has nothing to do with monks.  TRAPPIST is the acronym for the telescope’s rather long name.  Confirmation of all the planets, their sizes and mass was carried out by NASA’s Spitzer Infrared Telescope trailing the Earth in solar orbit.  Needless to say this star system will be the object of intense study as larger and more sophisticated ground and space based telescopes come on line in the next few years.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

TRAPPIST-1 vs inner solar system

Comparison of the TRAPPIST-1 planetary system with our own inner solar system.   The green zone is the habitable or Goldilocks zone Credit: NASA/JPL-Caltech/R. Hurt, T. Pyle (IPAC)

Planetary statistics

What is currently known about the TRAPPIST-1 Planets. Comparison of the TRAPPIST-1 planetary system with our own inner solar system. Credit: NASA/JPL-Caltech/R. Hurt, T. Pyle (IPAC)

Note that the surface features of these planets are in the eye of the illustrator.  They are currently black shadows seen on the face of the star that they cross.

Planet g looks closest to the Earth’s density of the habitable zone planets.  The problem I’d have is if I lived there at 12.35 days per year I’d be 2220 years old.

Entice your great-great-great-great grandkids with this travel poster:

Travel Poster

Planet Hop from TRAPPIST-1e. Maybe not next door like Proxima b, but just down the block. only 39 light years away.

For more information:

On the Spitzer site you can find:
Images
Videos (b-roll and annotated/narrated)
Planet surface maps and starfield backdrop image
http://www.spitzer.caltech.edu/trappist-1

On the JPL site you can also find:
Exoplanet Travel Poster
VR tour of TRAPPIST-1d surface
Additional videos
https://exoplanets.nasa.gov/trappist1/

On the ESO site you can also find:
Even more videos and graphics
http://www.eso.org/public/news/eso1706

Play around with the TRAPPIST-1 and other extra solar planetary systems with NASA’s Eyes:  https://eyes.nasa.gov/eyes-on-exoplanets.htm.

Replay the news conference announcing the TRAPPIST-1 discovery from February 22, 2017:
http://www.ustream.tv/recorded/100200725.

 

12/05/2016 – Ephemeris – The planet’s name is Dagon

December 5, 2016 Comments off

Ephemeris for Monday, December 5th.  The Sun will rise at 8:04.  It’ll be up for 8 hours and 57 minutes, setting at 5:02.  The Moon, 2 days before first quarter, will set at 11:02 this evening.

The lonely bright star low in the south-southwest at 8 p.m. these evenings is Fomalhaut the harbinger of autumn in my book, and about to leave as winter approaches.  Fomalhaut means fishes mouth and is located at the head of Piscis Austrinus, a very dim constellation.  Fomalhaut is a young white star only about 400 million years old with a disk of dust surrounding it.  Near an outer dust ring, 14 years ago the Hubble Space Telescope discovered a spot.  Four years later astronomers discovered that the spot moved along the dust lane and announced the first direct discovery of an exoplanet.  In 2010 and 2012 the planet now dubbed Fomalhaut b or Dagon was observed again and it really does orbit Fomalhaut in a very eccentric orbit.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Fomalhaut b

The track of observations of Fomalhaut b or Dagon in 2004, 2006, 2010 and 2012. Credit: NASA and ESA.

11/15/2016 – Ephemeris – Imaging exoplanets from the ground

November 15, 2016 Comments off

Ephemeris for Tuesday, November 15th.  The Sun will rise at 7:40.  It’ll be up for 9 hours and 33 minutes, setting at 5:14.  The Moon, 1 day past full, will rise at 6:43 this evening.

There’s something I never thought I’d see in my lifetime was a telescope on the ground that could image planets around other stars.  Remember that planets shine by reflecting the light of their host stars, and due to their distance of many trillion of miles away, that there would be no hope of separating the planet from the star which is billions of times brighter.  My lifetime includes the launch of Sputnik, the first artificial satellite when I was in the 11th grade.  However with huge telescopes with adaptive optics that take the wiggle out of the atmosphere.  Added to that is the CHARIS instrument on the 8.2 meter Subaru telescope on Mauna Kea in Hawai’i, which not only can see exoplanets around stars, but take their spectra, to analyze chemical compounds in their atmospheres.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

CHARIS image

A plot of data from CHARIS shows planets located around a star in the planetary system HR8799. (Images courtesy of N. Jeremy Kasdin and the research team)

The story is here:
http://www.princeton.edu/main/news/archive/S47/82/89C62/?section=topstories

08/16/2016 – Ephemeris – Does Proxima Centauri have a planet? Also some information for southern observers about Mercury

August 16, 2016 Comments off

Ephemeris for Tuesday, August 16th.  The Sun rises at 6:46.  It’ll be up for 13 hours and 59 minutes, setting at 8:46.  The Moon, 2 days before full, will set at 5:53 tomorrow morning.

Proxima Centauri is the closest star to our solar system.  It is a red dwarf star, and a distant third member of the Alpha Centauri star system.  Recently the German weekly Der Spiegel announced that astronomers at the La Silla Observatory in Chile have detected a possible Earth-like planet at a distance that water may be liquid on its surface around this tiny star.  Other than this one leak, no one is talking, and the European Southern Observatory is mum on the subject.  There may be some kind of announcement at the end of the month.  If true, this means that the closest earth-like planet orbits the closest star, only four and a quarter light years away.   That’s nearly 25 trillion miles, and hundreds of years travel time with our current technology.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Proxima Centauri chart

Chart showing the location of Proxima Centauri, labeled here HIP 70890. Alpha Centauri is labeled Rigel Kentaurus. Alpha Centauri is actually a catalog name in the style of Johann Bayer’s 1603 star atlas. Note also the alpha (α) Greek letter next to the star. Created using Cartes du Ciel (Sky Charts).

Note also the star labeled Agena.  That is the more distant Beta (β) Centauri also known as Hadar.

Proxima Centauri image

A section of a photograph of part of the field of view of the chart above. Credit: Wikipedia user Skatebiker.

Extra

For our southern observers:  Today Mercury reaches its greatest eastern elongation  of 27 degrees.  So it’s visible in the west with Venus and Jupiter.