I have had two people ask me about this internet story making the rounds. Here is the story, and how I answered it:
ORIGINAL STORY
For all you amateur astronomers out there:
A Must See This Summer - MARS SPECTACULAR!
The Red Planet is about to be spectacular! This month and next,
Earth is catching up with Mars in an encounter that will culmin-
ate in the closest approach between the two planets in recorded
history. The next time Mars may come this close is in 2287.
Due to the way Jupiter's gravity tugs on Mars and perturbs its
orbit, astronomers can only be certain that Mars has not come
this close to Earth in the Last 5,000 years, but it may be as
long as 60,000 years before it happens again.
The encounter will culminate on August 27th when Mars comes
to within 34,649,589 miles of Earth and will be (next to the
moon) the brightest object in the night sky.
Mars will look as large as the full moon to the naked eye.
Mars will be easy to spot. At the beginning of August it
will rise in the east at 10p.m. and reach its azimuth about
3 a.m.
By the end of August when the two planets are closest, Mars
will rise at nightfall and reach its highest point in the sky at
12:30 a.m. So, mark yourcalendar at the beginning of August to see Mars grow progres-
sively brighter and brighter throughout the month.
Yes, Mars is visible. But it will not be all that spectacular. There is a lot of misinformation going on here.
My Sister asked if this will be visible from Poland (where she is headed next month):
My response:
Mars is visible from everywhere on earth as long as it is night and Mars is not within about fifteen degrees of the sun.
Mars is well away from the sun right now, and is clearly visible in the night sky. (And this is true for Poland as well as USA)
As Mars goes around in its orbit, further out from the sun than ours, it takes a bit more than a couple of our years to return to the roughly same point in space. The earth, on a shorter orbit because we are closer to the sun, takes only one earth year to do the same. SO, we run around the track on our orbit, and in a year get back to the same place where we saw Mars best last time--but Mars has scooted around on its orbit, and is on the far side of its "lap" around the sun. We continue zipping along, and finally (after I think 26 months) catch up and "lap" Mars. This is as close as we get to it. When we are as close to it as possible (called "opposition") it is opposite the sun in our sky--in other words, it is highest at midnight. Since it is closest, it is also largest, and brightest it ever gets. And since it is directly opposite the sun, we catch its full face shiniing back on us.
The moon is about 30 arc minutes across on average. Sometimes it is a little closer, and sometimes further away, and so it varies by about 5 arc minutes overall. Mars, however, since it is very much farther away from us when it is on the other side of the sun than when it is on the same side (at opposition) varies from about 14 arc SECONDS to about 25 arc SECONDS. So, Mars will be almost twice as large at opposition as it is when on the far side of the sun. But (since there are sixty arc seconds in an arc minute (and incidentally, sixty arc minutes in a degree, and 360 degrees in a circle), it will still be smaller than one sixtieth of the size of the moon.
This gets even more complicated because the orbits of Mars and the earth are elliptical (oval) rather than round, and sometimes, Mars is closer to the sun than at other times (just as Earth is). When Mars is at is perihelion (closes to the sun) and earth is at its aphelion (furthest from the sun), and Mars happens to be at opposition, then that is the largest possible that Mars can appear to earth observers. That nearly happened two years ago, on August 27th. THe next opposition will not be so favorably placed in regards to the closeness of Mars to the sun. (Incidentally, I believe Mars wat a perihelion last Saturday.)
SO--
Whoever is reporting this over the internet has made several errors:
One is that they used the date of the closest approach from the last oppostion as the big date. August 27 of 2003 was the closest approach of the two planets in several thousand years before or after. This upcoming opposition, which happens I think November something, or maybe late October (--I could look it up!) is a close one, but not as close as two years ago.
Secondly, they confused arc minutes--which is what the moon is measured in--with arc seconds--which is what the planets are measured in. And that makes the moon about 60 times the size of Mars.
So--Mars will look like a pretty bright star, but nothing special to the casual observer.
ORIGINAL STORY
For all you amateur astronomers out there:
A Must See This Summer - MARS SPECTACULAR!
The Red Planet is about to be spectacular! This month and next,
Earth is catching up with Mars in an encounter that will culmin-
ate in the closest approach between the two planets in recorded
history. The next time Mars may come this close is in 2287.
Due to the way Jupiter's gravity tugs on Mars and perturbs its
orbit, astronomers can only be certain that Mars has not come
this close to Earth in the Last 5,000 years, but it may be as
long as 60,000 years before it happens again.
The encounter will culminate on August 27th when Mars comes
to within 34,649,589 miles of Earth and will be (next to the
moon) the brightest object in the night sky.
Mars will look as large as the full moon to the naked eye.
Mars will be easy to spot. At the beginning of August it
will rise in the east at 10p.m. and reach its azimuth about
3 a.m.
By the end of August when the two planets are closest, Mars
will rise at nightfall and reach its highest point in the sky at
12:30 a.m. So, mark yourcalendar at the beginning of August to see Mars grow progres-
sively brighter and brighter throughout the month.
Yes, Mars is visible. But it will not be all that spectacular. There is a lot of misinformation going on here.
My Sister asked if this will be visible from Poland (where she is headed next month):
My response:
Mars is visible from everywhere on earth as long as it is night and Mars is not within about fifteen degrees of the sun.
Mars is well away from the sun right now, and is clearly visible in the night sky. (And this is true for Poland as well as USA)
As Mars goes around in its orbit, further out from the sun than ours, it takes a bit more than a couple of our years to return to the roughly same point in space. The earth, on a shorter orbit because we are closer to the sun, takes only one earth year to do the same. SO, we run around the track on our orbit, and in a year get back to the same place where we saw Mars best last time--but Mars has scooted around on its orbit, and is on the far side of its "lap" around the sun. We continue zipping along, and finally (after I think 26 months) catch up and "lap" Mars. This is as close as we get to it. When we are as close to it as possible (called "opposition") it is opposite the sun in our sky--in other words, it is highest at midnight. Since it is closest, it is also largest, and brightest it ever gets. And since it is directly opposite the sun, we catch its full face shiniing back on us.
The moon is about 30 arc minutes across on average. Sometimes it is a little closer, and sometimes further away, and so it varies by about 5 arc minutes overall. Mars, however, since it is very much farther away from us when it is on the other side of the sun than when it is on the same side (at opposition) varies from about 14 arc SECONDS to about 25 arc SECONDS. So, Mars will be almost twice as large at opposition as it is when on the far side of the sun. But (since there are sixty arc seconds in an arc minute (and incidentally, sixty arc minutes in a degree, and 360 degrees in a circle), it will still be smaller than one sixtieth of the size of the moon.
This gets even more complicated because the orbits of Mars and the earth are elliptical (oval) rather than round, and sometimes, Mars is closer to the sun than at other times (just as Earth is). When Mars is at is perihelion (closes to the sun) and earth is at its aphelion (furthest from the sun), and Mars happens to be at opposition, then that is the largest possible that Mars can appear to earth observers. That nearly happened two years ago, on August 27th. THe next opposition will not be so favorably placed in regards to the closeness of Mars to the sun. (Incidentally, I believe Mars wat a perihelion last Saturday.)
SO--
Whoever is reporting this over the internet has made several errors:
One is that they used the date of the closest approach from the last oppostion as the big date. August 27 of 2003 was the closest approach of the two planets in several thousand years before or after. This upcoming opposition, which happens I think November something, or maybe late October (--I could look it up!) is a close one, but not as close as two years ago.
Secondly, they confused arc minutes--which is what the moon is measured in--with arc seconds--which is what the planets are measured in. And that makes the moon about 60 times the size of Mars.
So--Mars will look like a pretty bright star, but nothing special to the casual observer.
