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Posts Tagged ‘Perihelion’

01/06/2020 – Ephemeris – The Earth was closest to the Sun in its orbit yesterday

January 6, 2020 Comments off

Ephemeris for Monday, January 6th. Today the Sun will be up for 8 hours and 57 minutes, setting at 5:17, and it will rise tomorrow at 8:19. The Moon, half way from first quarter to full, will set at 5:02 tomorrow morning.

Yesterday’s perihelion, or closest point of the Earth to the Sun of roughly 91.4 million miles (147 million km) is only 1.7% closer to the Sun than average. It doesn’t do much to make our winters warmer, but it does make winter the shortest season. That’s because the Earth travels faster when near the Sun than when it’s farther away. Winter lasts only 89 ½ days. The Earth’s aphelion, when it’s farthest from the Sun will be on the 4th of July, in summer, making that the longest season at 93 ½ days. Of course being this far north it feels like winter is longer than summer, but astronomically it’s the other way around. Being a leap year, with February having 29 days, spring will arrive a calendar day early on the 19th of March.

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

Addendum

Earth's orbit

The Earth’s orbit, somewhat exaggerated, showing perihelion and the seasons. Credit “Starts with a Bang” blog by Ethan Siegel.

Seasons for 2020

The Seasons for 2020 from data in Astronomical Tables of the Sun, Moon, and Planets Third Edition by Jean Meeus. Date and times are in TD, Dynamical Time. Subtract about 1 minutes to convert to Universal Time (UT).  Also subtract 5 hours for Eastern Standard Time and 4 hours for Eastern Daylight Time.

For and explanation of the Cross-Quarter Days column, check out my Ground Hog Day post last year:  https://bobmoler.wordpress.com/2019/02/02/02-02-2019-ephemeris-extra-groundhog-day-and-other-seasonal-days/

 

01/03/2020 – Ephemeris – Astronomical events this weekend

January 3, 2020 Comments off

Ephemeris for Friday, January 3rd. The Sun will rise at 8:20. It’ll be up for 8 hours and 54 minutes, setting at 5:14. The Moon, 1 day past first quarter, will set at 1:49 tomorrow morning.

Tonight at 8 p.m. there will be a telescope clinic by the Grand Traverse Astronomical Society at the Rogers Observatory south of Traverse City on Birmley Road for those who have either received a telescope for Christmas or have one hidden away in an attic, to learn how to use it. Bring ‘em if you’ve got ‘em.

Tomorrow morning we’ll see the peak of the Quadrantid meteor shower after the Moon sets. The radiant for this shower is near the handle of the Big Dipper, though they will be seen all over the sky. The peak should be around 3:20 a.m. with the possibility of over a hundred meteors visible per hour.

On Sunday at 5 a.m. the Earth will be its closest to the Sun for the year of 91,394,000 miles (147,085,000 km).

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

Addendum

Quadrantid radiant

The location of the Quadrantid radiant at 3:20 a.m. January 4, 2020 for the peak of the meteor shower. Created using Stellarium.

Earth's orbit

The Earth’s orbit, somewhat exaggerated, showing perihelion and the seasons. Credit “Starts with a Bang” blog by Ethan Siegel.

01/02/2018 – Ephemeris – Cozying up to the Sun and a major meteor shower

January 2, 2018 Comments off

Ephemeris for Tuesday, January 2nd. The Sun will rise at 8:20. It’ll be up for 8 hours and 53 minutes, setting at 5:13. The Moon, 1 day past full, will rise at 6:18 this evening.

Today the Earth will reach its closest distance from the sun, of 91.4 million miles. This point in Earth’s orbit is called perihelion. The Earth varies about 3 million miles from perihelion to aphelion its farthest point from the sun, which usually occurs around July 4th or 5th. Perihelion doesn’t help warm our winters though, but it does make winter the shortest season because the Earth moves its fastest at perihelion. That makes summer the longest season by several days. Tomorrow afternoon will see the peak of the Quadrantid Meteor Shower. This active meteor shower has its radiant north of the kite shape of Boötes and near the handle of the Big Dipper but the bright Moon will interfere both tomorrow and Thursday mornings.

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

Addendum

Earth's orbit

The Earth’s orbit, somewhat exaggerated, showing perihelion and the seasons. Credit “Starts with a Bang” blog by Ethan Siegel.

While a planet’s distance from the Sun modify the seasons somewhat, seasons are always governed by the axial tilt of the planet with respect to the Sun.

Quadrantid Radiant

Facing the Quadrantid radiant at 6 a.m. January 3rd. Created using my LookingUp program.

01/03/2017 – Ephemeris – The Earth will be closest to the Sun tomorrow

January 3, 2017 Comments off

Ephemeris for Tuesday, January 3rd.  The Sun will rise at 8:19.  It’ll be up for 8 hours and 55 minutes, setting at 5:15.  The Moon, 2 days before first quarter, will set at 11:06 this evening.

The Earth has as elliptical orbit of the Sun, as do all planets.  It is close to circular but not quite.  The Earth’s distance from the Sun is 93 million miles (150 million km) plus or minus a million and a half miles.  Tomorrow at about 6 a.m. the Sun will be at a point called perihelion, only 91.4 million miles (147 million km).  It makes only a tiny difference in the Sun’s intensity, but since the Earth moves faster when closest to the Sun, it makes winter the shortest season at 89 days.  Aphelion, Earth’s farthest distance from the sun occurs around July 4th which makes summer the longest season at 93 days.  The eccentricity of an orbit can modify the seasons, but the seasons themselves are caused by the tilt of the planet’s axis alone.

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

Addendum

Earth's orbit

The Earth’s orbit, somewhat exaggerated, showing perihelion and the seasons. Credit “Starts with a Bang” blog by Ethan Siegel.

Categories: Ephemeris Program, Seasons Tags:

01/01/2016 – Ephemeris – Happy New Year – It’s a busy few days to start off the year

January 1, 2016 Comments off

Happy New Year.  This is Bob Moler with Ephemeris for New Years Day, Friday, January 1st, 2016.  The Sun will rise at 8:20.  It’ll be up for 8 hours and 52 minutes, setting at 5:12.   The Moon, 1 day before last quarter, will rise at 12:54 tomorrow morning.

It’s always a busy time, astronomically speaking, around the start of the year.  This year even more so.  Comet Catalina is found near the bright star Arcturus now, which is a good way to find it in binoculars.  Tomorrow at 7:59 p.m. (1:59 UT 3rd) the Earth will reach perihelion, the closest point in its orbit to the Sun at about 91.4 million miles (0.9833 AU).  It doesn’t add much to the heat we get from the Sun, but it does make winter a couple of days shorter than summer.  Monday at 3 a.m. will see the peak of the Quadrantid meteor shower.  Unfortunately that’s about the time the Moon will rise.  The radiant is north of the handle of the Big Dipper.  Good news:  tomorrow is the latest sunrise, it should be rising earlier until June.

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

Addenda

January Star Chart

Javnuary Star Chart

Star Chart for January 2016. Created using my LookingUp program. To enlarge in Firefox Right-click on image then click View Image.

The planets and stars are plotted for the 15th at 9 p.m. EST.  That is chart time.  Note, Traverse City is located 45 minutes behind our time meridian.  To duplicate the star positions on a planisphere you may have to set it to 45 minutes earlier than the current time.

Evening astronomical twilight ends at 6:22 p.m. EST on January 1st, increasing to 6:55 p.m. EST on the 31st.

Morning astronomical twilight starts at 7:09 a.m. EST on January 1st, and decreasing to 6:57 a.m. EST on the 31st.

Add a half hour to the chart time every week before the 15th and subtract and hour for every week after the 15th.

For a list of constellation names to go with the abbreviations click here.

  • Pointer stars at the front of the bowl of the Big Dipper point to Polaris the North Star.
  • QuadR is the Quadrantid meteor shower radiant

Calendar of Planetary Events

Credit:  Sky Events Calendar by Fred Espenak and Sumit Dutta (NASA’s GSFC)

To generate your own calendar go to http://eclipse.gsfc.nasa.gov/SKYCAL/SKYCAL.html

Times are Eastern Time.  Some additions made to aid clarity.

     Date   Local      Event
            Time EST
Jan  01  Fr            Venus: 37.9° W
     02  Sa 12:30 a.m. Last Quarter
     02  Sa  6:53 a.m. Moon Apogee: 404300 km
     02  Sa  7:59 p.m. Perihelion: 0.9833 AU
     03  Su  1:45 p.m. Moon-Mars: 1.6° S
     04  Mo  3:01 a.m. Quadrantid Shower: ZHR = 120
     06  We  6:57 p.m. Moon-Venus: 3.3° S
     06  We 11:57 p.m. Moon-Saturn: 3.6° S
     07  Th  6:32 a.m. Venus-Antares: 6.4° N
     08  Fr 12:56 p.m. Moon South Dec.: 18.4° S
     09  Sa  2:42 a.m. Venus-Saturn: 0.1° N
     09  Sa  8:30 p.m. New Moon
     14  Th  9:02 a.m. Mercury Inferior Conj.
     14  Th 10:48 a.m. Moon Descending Node
     14  Th  9:10 p.m. Moon Perigee: 369600 km
     16  Sa  6:26 p.m. First Quarter
     19  Tu  9:16 p.m. Moon-Aldebaran: 0.5° S (Occultation*)
     21  Th 11:41 a.m. Moon North Dec.: 18.4° N
     23  Sa  8:46 p.m. Full Moon
     26  Tu 12:10 a.m. Moon-Regulus: 2.8° N
     27  We  6:58 p.m. Moon Ascending Node
     27  We  8:14 p.m. Moon-Jupiter: 1.6° N
     30  Sa  4:10 a.m. Moon Apogee: 404600 km
     31  Su 10:28 p.m. Last Quarter
Feb  01  Mo            Venus: 31.4° W

* Occultation of Aldebaran For the Grand Traverse Area ± 1-2 minutes:
Disappearance 9:06 p.m.  Reappearance 10:25 p.m.  I’ll have more information on the 19th.

Occultation Map

Occultation Map

Occultation visibility map for January 20, 2016 (UT). Credit IOTA/Occult4 program.

Estimating occultation timings for your location

I used Cartes du Ciel the free software that I have a link to on the right.  Make sure that the program is set for topocentric positions under Setup/Solar System.  And you have entered your position under Setup/Observatory.  You can find your location in Google Earth, or your GPS device or smart phone.

You can also use Stellarium.  Just make sure the Moon is normal sized.

In both programs you can lock the Moon or Aldebaran in the center of the screen Pick a time in advance of the occultation and using the set time window walk the star towards the Moon, mark the time.  Then walk the star out from the Moon and record the reappearance time.  That’s it.

This should work with other planetarium programs too.

For better accuracy go to the International Occultation Timing Association (IOTA) website.  Download and install their Occult4 program for Windows computers.  Follow the instructions.  When I ran the program for my location, the location I use for Interlochen/Traverse City (Since I live approximately half-way between the two).  I got results within a half-minute of the IOTA Occult4 program results.  So the approximation method using these planetarium programs is valid.

Comet C/2013 US10 (Catalina)

Comet Catalina January 2016

The track of Comet C/2013 US10 (Catalina) for January 2016. Created using Cartes du Ciel (Sky Charts).

The comet is roughly one magnitude fainter than given.  Comet is plotted every day at 4 a.m. EST (9 hr UT) with the date and magnitude labeled every 5th day.  According to the brightness graph the comet began to under perform in brightness back in September, however, according to a new brightness formula the comet may increase in brightness by a magnitude by late February when it will be well placed for viewing all night. To monitor the brightness reports from observers go to http://www.aerith.net/comet/catalog/2013US10/2013US10.html.

xxxvvvvv

07/06/2015- Ephemeris – Today we are at our greatest distance from the sun.

July 6, 2015 Comments off

Ephemeris for Monday, July 6th.  Today the Sun will be up for 15 hours and 26 minutes, setting at 9:30.   The Moon, 2 days before last quarter, will rise at 12:23 tomorrow morning and tomorrow the Sun will rise at 6:04.

This is the day the we are the farthest we can get from the Sun for the year.  The point in the Earth’s orbit that it occurs is called aphelion.  Earth is closest to the Sun in January at perihelion.  The actual distance difference between perihelion and aphelion is 3 million miles out of roughly 93 million miles.  So now we’re roughly 94 and a half million miles from the Sun or 152 million kilometers., and will swoop down to 91 and a half million miles(91.4) or 147 kilometers from the Sun in early January.  Because Earth’s northern and southern hemispheres have different ratios and placement of land versus ocean I’m not sure you could correlate seasonal differences of the hemispheres with the Earth’s distance from the Sun.  Anyway the approximate time we reach aphelion will be 3 p.m. EDT (19 hr UT).

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

Addendum

The orbits of the inner planets. (P)erihelion - (A)phelion

The orbits of the inner planets. (P)erihelion – (A)phelion

The above is a diagram from three years ago, so the planets other than the Earth will be in different positions today.  The date of aphelion and perihelion move around over a greater range of dates than the equinoxes and solstices.  I’m not sure why without researching it, but I suspect that the Moon has something to do with it.

01/02/2015 – Ephemeris – Telescope Clinic tonight in Traverse City

January 2, 2015 Comments off

Ephemeris for Friday, January 2nd.  The sun will rise at 8:20, the latest sunrise of the year.  It’ll be up for 8 hours and 53 minutes, setting at 5:13.   The moon, 2 days before full, will set at 6:38 tomorrow morning.

Did you or someone in your family get a telescope for Christmas, or have one in a closet or attic because you don’t know how to put it together or operate?  Or maybe you are trying to figure out which one to buy.  Well, tonight’s your night.  The Grand Traverse Astronomical Society will host a telescope clinic at Northwestern Michigan College’s Rogers Observatory on Birmley Road, south of Traverse City starting at 8 p.m.  Telescope experts from the society will help you set up your telescope and give you observing tips.  So bring ’em if you’ve got ’em.  If it’s clear, at 9 p.m., there will be a star party to try out your telescope, or try them out on the lights of Traverse City.  Can’t make it?  We can help you after any meeting.

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

Addenda

Remember the Quadrantid meteor shower tomorrow evening and into Sunday morning:

The moon will interfere with the meteor shower, so only the brightest will be visible.  The radiant will rise from the northeast.  The radiant will be nearly overhead at the start of twilight.  On a dark night up to 120 meteors per hour may be seen according to the International Meteor Organization.

Quadrantid meteor shower radiant at 1:30 a.m.

 

The Earth will reach perihelion Sunday.
This is the closest the Earth gets to the Sun in its orbit this year.  The Sun will be 91,402,000 miles or 147,096,000 kilometers away at around 1 a.m. January 4th, 2015 EST or 6 hr UT January 5th 2015.  It makes winter the shortest season because the Earth is moving its fastest during perihelion.  It’s only by a few days.  And in northern Michigan where it seems that winter overlaps half of fall and spring besides, that few days difference is buried under snow.