July’s full Buck Moon, the second full moon of summer in the Northern Hemisphere, will turn full on Wednesday (July 29). It will be the final full moon before a flurry of solar and lunar activity — notably, a total solar eclipse caused by the new moon on August 12, and a partial lunar eclipse during the following full moon on August 28.
Named for the new antlers that emerge from male deer during summer, July’s full moon is also known as the Thunder Moon and Hay Moon, according to Time and Date. The Anishinaabeg people call it Miin Giizis, or Berry Moon, according to the Center for Native American Studies.
The Buck Moon will be at its fullest at 10:37 a.m. EDT on Wednesday — however, it will also look bright and full on Tuesday and Thursday night. From North America, the best time to see it will be at moonrise in the southeast during dusk on Wednesday evening. The exact time of moonrise will depend on your location. A full moon looks most dramatic as it first appears above the eastern horizon shortly after sunset, with Rayleigh scattering making it loom orange — the same light-scattering phenomenon that makes the sky blue and sunsets red.
July's full moon is one of the lowest full moons of the year as seen from the Northern Hemisphere because it occurs relatively soon after the June solstice. A full moon always sits opposite the sun, so the path of July's full moon mirrors the sun's path in February.
Two weeks after theBuck Moon, the new moon will slide directly between Earth and the sun, causing a total solar eclipse. Observers along a narrow path of totality in eastern Greenland, western Iceland and northern Spain will see the moon block the sun for a few minutes, revealing the solar corona.
A deep partial solar eclipse will be visible across Europe, with a small partial solar eclipse observed over Canada and the northeastern U.S.. The largest eclipse in Canada will be 93% in northeastern Nunavut, while northeastern Maine in the U.S. will see 29% of the sun covered by the moon. Solar eclipse glasses must be worn at all times to safely view the partial phases.
The next full moon, the Sturgeon Moon, will rise on August 27 and be partially eclipsed by Earth overnight. More than 96% of the moon will pass into Earth's shadow as seen from Europe, Africa, North America and South America.
How much do you know about the moon? Test your lunar smarts with our moon quiz!
NASA’s Hubble Shows Star Formation in Andromeda Galaxy Winding Down
NASA Hubble’s view of part of the Andromeda galaxy.
Credits: Image: NASA, ESA, Benjamin Williams (UWashington), Zhuo Chen (UWashington), L. Clifton Johnson (Northwestern); Image Processing: Joseph DePasquale (STScI)
A new study using data from NASA’s Hubble Space Telescope finds that star formation in the nearby Andromeda galaxy has undergone a 500-million-year decline, with an even steeper drop in the last 40 million years. Andromeda, a spiral galaxy comparable in size to our Milky Way, is close enough to be seen with the unaided eye from areas with dark skies. Located about 2.5 million light-years from Earth, practically our cosmic backyard, Andromeda offers an opportunity for astronomers to examine its stellar populations in detail, leading to better understanding of the past of galaxies like our own.
To reach this conclusion, the researchers combined data from two Hubble surveys: the Panchromatic Hubble Andromeda Treasury and the Panchromatic Hubble Andromeda Southern Treasury. Together, these two surveys mapped two-thirds of the disk of Andromeda in ultra-sharp detail. In total, the team measured about 200 million individual stars across the galaxy, giving them a detailed picture of Andromeda’s past activity.
“We need to measure the individual stars because they are the fossil record of the galaxy’s formation. Hubble is the only telescope that can give you high enough spatial resolution over a large enough area to be able to do that in Andromeda,” said Ben Williams, astronomer at the University of Washington and a co-author on the study.
Massive stars are bluer and short-lived, while less massive stars are redder and longer-lived. As a result, areas that have experienced recent star formation tend to have a larger fraction of blue stars, while areas with less recent star formation typically have a redder population. The team divided the Andromeda images into thousands of squares, spanning 300 light-years on each side of the square, and determined the history of star formation within each parcel to gain a comprehensive view of the galaxy’s past.
NASA’s Hubble Space Telescope has provided a detailed view of millions of stars in the Andromeda galaxy. Regions that have experienced recent star formation (1) appear significantly bluer than regions with less recent star formation (2).
NASA, ESA, Benjamin Williams (UWashington), Zhuo Chen (UWashington), L. Clifton Johnson (Northwestern); Image Processing: Joseph DePasquale (STScI)
Steady decline
Previous research showed the Andromeda galaxy experienced a dramatic burst of star formation about 2 billion years ago, likely due to a past interaction or merger with another galaxy. Since that time, star formation has been steadily declining.
Astronomers measure the rate of star formation in terms of the mass, or amount of gas and dust, converted into stars per year. The researchers calculated that, 500 million years ago, Andromeda formed stars at a rate of about one solar mass per year. However, the formation rate dropped to about half that by 40 million years ago. The current rate has plummeted even farther, to about one-fifth the mass of our Sun per year.
The team also examined whether that decline was consistent across the galaxy or concentrated in certain areas. They found that much of the recent star formation has occurred in a star-forming ring located about 32,000 light-years from the galaxy’s center. As a result, much of the decline they measure is driven by decreasing activity within that ring.
Rather than being the result of reduced material from which new stars can form, the decline is more likely to be a natural winding down from its previous, more active state.
“It’s just like after running a marathon, sometimes you’ve got to take a bit of a breather,” said Tobin Wainer, lead author, University of Washington.
Likely suspect
The team also investigated whether there was any connection between the decrease of activity in Andromeda and its proximity to satellite galaxy M32 (Messier 32). The M32 galaxy is separated from Andromeda by about 16,000 light-years in the plane of the sky; however, its 3D location in space is uncertain. As a result, astronomers are unsure if or when it might have interacted with Andromeda in the past.
“One of the major motivations for this program was to probe potential interactions between M32 and Andromeda’s disk,” said Zhuo Chen, co-author, University of Washington.
Survey data from the Panchromatic Hubble Andromeda Southern Treasury allowed the team to study the history of star formation in Andromeda near M32. They found that this area showed signs of decreased star formation compared with other regions. The timing of this decrease, which this study finds began roughly 60 million years ago, could help constrain when the M32 galaxy interacted with Andromeda’s disk.
“We can’t explicitly say that we are seeing a decrease in star formation because of M32. But it’s right there, and it’s definitely the most likely suspect,” said Wainer.
This movie, created from an analysis of data from NASA’s Hubble Space Telescope, demonstrates how the rate of star formation in the Andromeda galaxy has declined over the past 500 million years. Brighter colors indicate where star formation was highest during a given time.
Visualization: Tobin Wainer (UWashington); Image Processing: Joseph DePasquale (STScI); Video: NASA, ESA, STScI, Gregory Bacon (STScI)
The team plans to continue analyzing the Hubble data and combine it with data from ground-based observatories to gain additional insights into the history of Andromeda.
“There’s a strong scientific value to this archival data. Andromeda is important because it’s a neighbor that is close enough that we can see it in great detail while also getting a global perspective,” said Raja GuhaThakurta, co-author, University of California Santa Cruz.
An even greater global perspective is likely to come from NASA’s Nancy Grace Roman Space Telescope after it launches as early as Sunday, Aug. 30. Roman’s gigantic field of view can cover at least 100 times as much area as Hubble at near-infrared wavelengths in a single observation. A newly approved Roman observing program will image the entirety of Andromeda’s disk and areas of its surrounding halo, allowing astronomers to measure hundreds of millions of stars and enabling groundbreaking new science.
The Hubble Space Telescope has been operating for more than three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the universe. Hubble is a project of international cooperation between NASA and ESA (European Space Agency). NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope and mission operations. Lockheed Martin Space also supports mission operations at Goddard. The Space Telescope Science Institute in Baltimore, which is operated by the Association of Universities for Research in Astronomy, conducts Hubble science operations for NASA.
NASA’s Hubble Space Telescope has provided a detailed view of millions of stars in the Andromeda galaxy.
Star Formation Rate in Andromeda Over Time
This movie, created from an analysis of data from NASA’s Hubble Space Telescope, demonstrates how the rate of star formation in the Andromeda galaxy has declined over the past 500 million years.
Two meteor showers will peak together overnight on Thursday, July 30, into Friday, July 31 — but skywatchers should expect a moonlit challenge rather than a dazzling display.
Both the Southern Delta Aquariids and the Alpha Capricornids reach maximum activity just one night after July's full Buck Moon, which turns full on Wednesday, July 29. According to the American Meteor Society, the moon will still be 98% full during the peaks of those meteor showers, meaning bright moonlight will wash out many of the fainter "shooting stars."
This year, the Southern Delta Aquariids are active from July 12 to Aug. 23 and peak on the night of July 30-31. The meteor shower can result in about 25 shooting stars under ideal dark skies, but the full moon makes this year's timing far from perfect. The Alpha Capricornids, which are active from July 3 to Aug. 15 this year, offer around five meteors per hour on the same peak night. That's not many, but the Alpha Capricornid meteor shower is known for bright fireballs — space rocks that shine brightly, and sometimes colorfully, as they catch fire during the plunge through Earth’s atmosphere.
From North America, the moon will appear bright for much of the night around the meteor showers' peak. A nearly full moon does not stop meteors from occurring, but it brightens the sky enough to hide the faintest streaks. That's particularly important for the Southern Delta Aquariids, which can be faint and typically lack fireballs, according to the American Meteor Society. Even still, the overlapping showers make a great night for practicing your meteor shower photography or for taking pictures of the moon.
The best time to try watching will be between midnight and dawn, when the radiant — the point from which the meteors seem to emanate — of the Southern Delta Aquariids, the constellation Aquarius, is highest in the southern sky. Observers in the southern U.S., Mexico and the Caribbean will be better placed than those farther north because Aquarius climbs higher at lower latitudes.
For the best chance of seeing some shooting stars, keep the moon behind you or blocked by a building, tree or hill, and look toward the darkest part of the sky. Meteor showers are always best viewed with the naked eye.
If you're clouded out — or mooned out — during the July meteor peaks, don't worry, as you'll get a better opportunity in August. The Perseid meteor shower will peak overnight on Aug. 12-13, just after the Aug. 12 new moon, when skies will be moonless for the meteor shower's peak rate of 100 meteors per hour.
That same new moon will also cause a total solar eclipse to be visible along a narrow path through eastern Greenland, western Iceland and northern Spain. A partial solar eclipse will be seen from parts of Canada and the northeastern U.S. (Remember to protect your eyes with proper solar eclipse glasses at all times during the partial phases.)
The combination of a solar eclipse and the peak of a major meteor shower will make Aug. 12-13 potentially one of the most exciting days of the year for skywatchers.
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