Happy aphelion!

By Phil Plait | July 5, 2012 10:59 am

Today – July 5, 2012 – at about 04:00 UTC (a few hours ago as I write this) the Earth reached aphelion, the point in its elliptical orbit when it’s farthest from the Sun.

According to the US Naval Observatory, we were 1.016675058 Astronomical Units from the Sun at that time. An AU is the average distance from the Earth to the Sun, and is defined as 149,597,870.7 kilometers (92,955,807.2 miles).

That means that at aphelion the center of the Earth was 152,092,424 km (94,505,851 miles) from the center of the Sun.

Over the next six months we’ll slowly approach the Sun again until we reach perihelion – the closest point in the Earth’s orbit to the Sun – on January 2, 2013, at about 05:00 UTC.

When we’re farther from the Sun it appears a little bit smaller in the sky, but you’d never notice. For one thing, staring at the Sun is a bad idea! For another, the change is so slow day by day that it’s impossible to notice anyway. For a third thing, the total change over the course of six months isn’t very big either. Astronomer (and friend of the blog) Anthony Ayiomamitis took two pictures that show this:

These are from aphelion and perihelion in 2005, but the scale is always about the same every year. As you can see, the change in the Sun’s size isn’t terribly big.

So even though you may not notice it, it’s still neat to think that after the past 183 days or so we’ve been steadily moving farther from the Sun, and now we’re on our way back in. And even neater… the Earth has done this over four and half billion times before. So it has some experience here.


Related Posts:

- Perihelion: The Earth is on its way back out again
- Top o’ the orbit to ya!
- Does the Sun look smaller to you?
- Does this perihelion make my Sun look fat?

CATEGORIZED UNDER: Astronomy, Cool stuff

Comments (25)

  1. Timmy

    “Perihelion”? I think you mean SUPERSUN!
    Dun Dun DUUUUUNN!!

  2. carbonUnit

    Funny how the distance is opposite northern hemisphere seasons…

  3. And just last night, the Twilight Zone episode “Midnight Sun” was on TV. :-)

  4. Joesixpack

    That’s quite a coincidence Ken B, I was just talking to my brother about that very same episode of Twilight Zone a couple of days ago.

    I used to be surprised by coincidences like this, but then I realized that a world without coincidence would be a much stranger place.

  5. I don’t care how much “experience” you claim the Earth has. I still want to see its original, long-form birth certificate.

  6. “Funny how the distance is opposite northern hemisphere seasons…”

    What’s funny about it? It merely demonstrates that axial tilt is the main cause of the seasons.

  7. I was also thinking about that Midnight Sun episode. Just because it’s so frakking HOT everywhere!

  8. #2 CarbonUnit:
    Why is it “funny”? The seasons have precisely nothing to do with the Earth’s distance from the Sun.

  9. Off-topic, but worth it. Surprised you haven’t mentioned it.

    https://www.facebook.com/Milkyway.Nasa

  10. carbonUnit

    Yes, I understand that, just making fun of those who think the distance causes seasons/accounts for warming.

  11. Trebuchet

    “These are from aphelion and perihelion in 2005, but the scale is always about the same every year. As you can see, the change in the Sun’s size isn’t terribly big.”

    I think you mean “apparent size”. (End of nitpick!)

  12. MadScientist

    Now that you’ve shown how the apparent size varies, how about convincing folks that the sun isn’t quite round – after all, that’s been known for many decades.

  13. AstroLad

    I remember about 30 years ago some Jehovah’s Witnesses telling me that the Earth would burn up or freeze if the distance to the sun changed by only 50 miles. It had to be God that made the orbit so perfect. Back then I was more polite to crazies than I am now so I did not fall down laughing.

  14. For those of us in the USA, this occurred in the evening of July 4, while we were watching fireworks. 9 PM on the left coast, around midnight on the right side.

  15. Kevin

    #6,9 way to keep it on topic here. You clearly are the smartest people on earth. *slow clap*

  16. Kevin

    #10 That link merely demonstrates that you are easily amused

  17. Ross

    Hopefully tomorrow we can see your take on this:

    http://www.bostonherald.com/news/national/general/view/20120705dark_matter_filament_found_scientists_say

    “Now, after much searching and with a little luck, an international team of astrophysicists has discovered a dark matter filament connecting two clusters of galaxies about 2.7 billion light-years away.”

  18. Naomi

    I’d say something cynical about, “The Earth is at its furthest point from the sun? It FEELS it!”, but we all know that has nothing to do about it…

    (Seriously, anyone in the northern hemisphere want to swap weather? You can have a crisp eight degrees celsius and I can be WARM!)

  19. J

    Oh, this explains why it was so unusually cold yesterday :-)

  20. Peter B

    Naomi @ #19 said: “(Seriously, anyone in the northern hemisphere want to swap weather? You can have a crisp eight degrees celsius and I can be WARM!)”

    Eight degrees? Oh, I’d love that. How do you like -6 degrees overnight? And we’re not even into the coldest month of the year here in Canberra. Come on, this is Australia, not Canada!

  21. Nigel Depledge

    Naomi (19) said:

    Seriously, anyone in the northern hemisphere want to swap weather? You can have a crisp eight degrees celsius and I can be WARM!)

    You can have our British summer this year. It’s a little bit damper than usual (the flash floods are not a normal part of the British summer, honest!), but with temps in the range of 16 – 20 °C it’s also a wee bit cooler than usual.

  22. Turboblocke

    The difference in distance between aphelion and perihelion is about 3%. IIRC power over the surface area of the Earth is proportional to the inverse of the cube of distance, so currently average energy from the Sun reaching the Earth is about 91% of the maximum. So it definitely isn’t the Sun that’s (directly)responsible for current heat waves.

  23. Robert Tulip

    #9 Neil Haggath
    “The seasons have precisely nothing to do with the Earth’s distance from the Sun.”

    Not true. Glacial maxima have occurred when December solstice was at perihelion. Milankovitch showed that ice age cycles are driven by the 21646 year cycle of precession of the seasons around the orbital ellipse, together with obliquity and ellipticity.

  24. Just be glad you don’t live on Mars.

    The difference between the Aphelion and Perihelion distances on Mars is on the order of a whopping 1.2-to-1! Your southern-hemisphere Winters and Summers would be that much more extreme!

    (Well, okay, you also wouldn’t have any breatheable air, and the temperature would be below freezing nearly everywhere. Details, details.)

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

ADVERTISEMENT

See More

ADVERTISEMENT
Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »