Galaxies

Until the 20th century, astronomers ignored the interiors of things. They had to. Telescopes only showed outermost layers.Scientists knew that a ball's "inside" constitutes virtually all its mass, but basic questions went unanswered: What, for example, lay below the dazzling solar surface? What mysteries might be found in the core of galaxies?

This year brings a rare lunar event called the Lunar Standstill, which happens only once every 18.5 years. Due to the Moon’s wobbling orbit aligning with Earth’s tilt, the Moon is reaching extreme positions in the sky. Recently, it appeared unusually low at first quarter, the third quarter Moon stood directly overhead—something typically impossible from the continental U.S. Even in daylight, the Moon remains high and visible, especially through sunglasses, offering a striking sight in the sky.

Vega, one of the brightest stars, is often mispronounced as "VAY-ga" but should be "WEE-ga," meaning "falling eagle" in Arabic. Visible at nightfall, it shines blue overhead, contrasting with the orange Arcturus. Located 25 light-years away, it’s 58 times brighter than the sun and spins much faster, completing a rotation in just 11 hours. In 12,000 years, Vega will become Earth's pole star. It also displays a rare blueshift, pointing to the direction we're traveling in space.

This week’s half Moon will appear unusually low in the sky—so low it might be hidden behind the trees. It sits far below its usual path due to the Moon’s wobbling orbit, which currently aligns with Earth’s tilt. This rare positioning, part of a cycle called the Lunar Standstill, places the Moon near the constellation Scorpius and its bright star Antares. Its light, filtered through thick atmosphere, may appear honey-colored and cast moonbeams at odd angles into places that rarely see moonlight. Look south to see this striking celestial oddity.

Arcturus: A Star Worth Saluting: On the next clear evening around 8 p.m., look west and halfway up the sky—you’ll spot Arcturus, a bright pastel-orange star and the fourth brightest we can see from Earth. It once famously opened the 1933 Chicago World's Fair with its light and is unique among bright stars for its wild, plunging path through space. Unlike stars that circle with the Milky Way, Arcturus is just passing through—so catch a glimpse while you can. It's the brightest thing in tonight’s sky… and it won’t be there forever.

On Wednesday, July 23, we saw a rare cosmic pairing as the Moon passes unusually close to Spica, the brilliant blue star in Virgo. Thanks to a unique tilt in the Moon’s orbit — an event that won’t repeat until 2043 — this striking alignment becomes visible to the naked eye. Learn why Spica shines so hot and bright, and how to pronounce its name the right way. Look up between 9:30 and 10 p.m. for a glimpse of this fleeting spectacle.

Twelve years ago, NASA's Curiosity rover journeyed to Mars with instruments that measured space radiation for the first time en route. The findings were sobering: astronauts would face radiation doses equivalent to a full-body CT scan every few days—raising cancer risks by 3–4% on the trip alone. Most of this came from galactic cosmic rays, which spacecraft walls can’t block. And this didn’t even include the added threat of solar storms. To send humans safely to Mars, solving the radiation challenge is essential.

Set your alarm early this week and look east between 5:00 and 5:30 a.m. to catch a stunning celestial display. Brilliant Venus, the Morning Star, shines high with the bright orange star Aldebaran glowing below. Aldebaran, part of the V-shaped Hyades cluster in Taurus, has a rich astronomical legacy—its position once helped confirm Einstein’s theory of General Relativity. Nearby, you’ll also spot the shimmering Pleiades cluster. Together, these stars create a breathtaking, layered view of the cosmos worth waking up for.

Celestial Visitor: Mars. You’ll see a bright "star" near the Moon, Mars — the planet long blamed for alien invasions in fiction. While Martian fears have faded, real space threats remain, like rogue asteroids. In 2013, one zipped past Earth while another exploded over Russia, injuring over a thousand. However, the ultimate doomsday scenario won’t come from space rocks, pandemics, or even climate change — it’ll come from our own Sun. In about 1.1 billion years, the Sun’s growing heat will boil Earth’s oceans, ending life as we know it. So, enjoy the night sky… while you can (you've got time).

There are two universes—the one we see, and the one we never will. The visible universe, just a sliver of the cosmos, ends where light can no longer reach us. Beyond that lies a possibly infinite realm—endless galaxies, stars, and mysteries forever out of reach. A groundbreaking study of 900,000 galaxies hints at this staggering vastness, suggesting that what we observe is zero percent of everything. An infinite universe could mean whole regions governed by unknown laws of physics. And if our view is that limited, can we trust the conclusions we’ve drawn? While science gives us solid facts, like the rotation of Mars, infinity challenges our grasp of the cosmos—and maybe that’s why it rarely makes the headlines.