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Moon and Antares

March 21, 2014

If you could leave Earth at a steady 25,000 miles an hour — the speed needed to escape our planet’s gravity — it would take you about 10 hours to reach the Moon. It would take about six weeks to reach our nearest planetary neighbor at its closest range. And it would take five months to reach the Sun.

Yet that distance is like a walk around the block compared to the size of the star Antares, which stands to the lower right of the Moon in the wee hours of tomorrow morning. It’s so big that at that same 25,000 miles an hour, you’d need almost three years to cross it.

Antares is so big because it’s also quite heavy — at least 15 times as massive as the Sun. That extra heft squeezes the star tightly, revving up the nuclear reactions in its core. The intense radiation pushes outward on the surrounding layers of gas, making them puff up like a giant balloon. As those layers expand they also get cooler, so the star’s surface glows reddish orange.

Now if you do a little quick arithmetic, you’ll see that something that’s hundreds of times wider than the Sun but only about 15 times heavier must be quite puffy. And in fact, Antares’s outer layers are so thin that they pretty much qualify as a vacuum. So with some shielding against the heat, your spacecraft could actually fly deep into Antares and survive.

Again, look for Antares not far from the waning gibbous Moon in the wee hours of tomorrow — a puffy supergiant of a star.


Script by Damond Benningfield, Copyright 2014

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